A typical example of the insulated gate bipolar transistor is illustrated in FIG. 1 of the drawings. The prior-art insulated gate bipolar transistor is of the lateral type and fabricated on an n-type semiconductor substrate 1. The insulated gate bipolar transistor comprises a heavily doped p-type drain region 2 and a p-type base region 3 both formed in the semiconductor substrate 1 in spacing relationship, a heavily doped n-type source region 4 and a heavily doped p-type source region 5 contiguous to each other and formed in the base region 3, and an insulating film 7 covering the surface of the semiconductor substrate 1. The insulated gate bipolar transistor further comprises a gate electrode 8 partially embedded into the insulating film 7 over those regions serving as the heavily doped n-type source region 4, the p-type base region 3 and the surface portion of the semiconductor substrate 1, so that the part of the insulating film 7 beneath the gate electrode 8 serves as a gate insulating film 9. In the insulating film 7 are formed contact windows one of which is filled with drain electrode 10 contacting the drain region 2 and the other of which allows a source electrode 11 to be in contact with the source regions 5 and 6.
In operation, an appropriate positive biasing voltage is applied to the gate electrode 8, an n-type channel takes place in the surface portion of the p-type base region 3 underneath the gate insulating film 7. Then, the n-type source region 4 and the surface portion of the n-type semiconductor substrate 1 are bridged by the n-type channel, and, for this reason, electrons flow from the n-type source region 4 into the semiconductor substrate 1. When the electrons are supplied to the semiconductor substrate 1, the semiconductor substrate 1 is decreased in potential level, so that the p-n junction between the p-type drain region 2 and the semiconductor substrate 1 is forwardly biased to inject holes into the semiconductor substrate 1. This hole injection results in reduction in resistance of the semiconductor substrate, and, accordingly, the insulated gate bipolar transistor is improved in on-resistance. Generally, an usual DMOS ( Double-diffused Metal Oxide Semiconductor ) device has a drawback in high resistivity of the semiconductor substrate, but the insulated gate bipolar transistor is free from the drawback inherent in the DMOS device.
However, a difficulty is encountered in the prior-art insulated gate bipolar transistor in implementation of an integrated complementary inverter circuit. Namely, the n-type semiconductor substrate is used for fabrication of the n-channel type insulated gate bipolar transistor illustrated in FIG. 1, and, on the other hand, a p-channel type insulated gate bipolar transistor is fabricated on a p-type semiconductor substrate. Then, the semiconductor substrates different in conductivity type should be provided for fabrication of the n-channel type and p-channel type insulated gate bipolar transistors, respectively. However, the complementary inverter circuit is implemented by using both the n-channel type insulated bipolar transistor and the p-channel type bipolar transistor but is allowed to use only one kind of semiconductor substrate. This difficulty is serious in high-speed push-pull circuits used in a pulse-width modulation for controlling an electric motor unit, because each of the transistors incorporated in the push-pull circuits be small in resistance on both of the source and sink sides such as the insulated gate bipolar transistor. However, each of the push-pull circuits is hardly fabricated on a single semiconductor chip, so that the circuits are implemented as discrete circuits. This results in increasing in production cost and in large amount of occupation space. The problem is also serious in an open-drain configuration incorporated in a solenoid-driver circuit and a display driver circuit. This is because of the fact that the drain region is liable to be equal in voltage level to the semiconductor substrate, then a self-isolation technique usually applied to a MOS ( Metal Oxide Semiconductor ) device is hardly employed to the integrated circuit formed by the insulated gate bipolar transistors of the lateral type.